PoS(MULTIF2019)023 https://pos.sissa.it/ s across multiple research fields, one of the most massive neutron ion star, we previously found that ith published evidence for super- stribution in light of this and more edback candidate). This shows that t massive neutron stars. Applying a the maximum mass of a neutron star. day) are a rapidly-growing pulsar pop- II - MULTIF2019 symmetric and not necessarily produced l wave astronomy. Compact binary mil- talunya, Av. Eduard Maristany 16, celona, Spain. (Linares, Shahbaz & Casares, 2018). We ⊙ . We find that four of them are compact binary ⊙ 0.16 M companion star, heated by the pulsar, and argue that ± ⊙ ive Commons onal License (CC BY-NC-ND 4.0). ab ∗ [email protected] reexamine the properties of the 0.33 M irradiation in this “redback” binary is extremeby yet an stable, extended source. We also reviewrecent the neutron discoveries. star mass We di compilemassive a neutron list stars, of with all masses (nine) above systems 2 M w compact binary millisecond pulsars are key to constraining millisecond pulsars (one black widow, two redbacks and one r the compact binary millisecond pulsarstars PSR J2215+5135 known hosts to date, with a mass of 2.27 new method to measure the velocity of both sides of the compan The maximum mass of a neutronincluding star astrophysics, has nuclear important physics implication and gravitationa lisecond pulsars (with orbital periods shorterulation, than about and a provide a good opportunity to search for the mos Speaker. ∗ Copyright owned by the author(s) under the terms of the Creat c Multifrequency Behaviour of High Energy Cosmic3-8 Sources June - 2019 XI Palermo, Italy Departament de Física, EEBE, Universitat PolitècnicaE-08019 de Barcelona, Ca Spain. Institute of Space Studies of CataloniaE-mail: (IEEC), E-08034 Bar Attribution-NonCommercial-NoDerivatives 4.0 Internati Manuel Linares Super-Massive Neutron Stars and Compact Binary Millisecond Pulsars

a b PoS(MULTIF2019)023 are max NS max NS Ss with s [13; 14]. Manuel Linares n 30 ms; see also [11]). core, and on the equation aries were discovered and , has important implications . However, compact binary , in one of only four compact ⊙ surements, discussing in depth ⊙ max NS ost global studies of the NS mass It is also important to know M studies [7; 8; 16], we know now distinction between neutron stars compact binary MSPs, which we come from rotation-powered radio NS has a critical impact on nuclear n 2 for definition and details). d narrow NS mass distribution near y, the EoS in the core and M .60; [10]), most of which are binary s on their masses before coalescing, densities close to and above nuclear as decrease its spin period and surface nd. Here, we review the most massive 0.12 M at supra-nuclear densities [7; 8; 9]. re recently, the maximum NS mass has uclear physics and gravitational wave d on the mass of the primary star, which ers and the associated GW emission [4]. er evolution in an interacting binary can black holes, in the new era of GW events ± ovae, when the proto-NS is being formed . In 2011, van Kerkwijk et al. [15] found s of a NS, which remain uncertain despite to avoid the uncertainties in correcting for ⊙ [1]. The birth masses of NSs depend on the light max NS 1 errors; see Table 1) obtained with different methods, σ NSs and ). Relatively incompressible matter (described by “stiff” 3 − 2% 1- ≃ massive [15; 17; 18; 19; 20]. g cm max NS 14 10 × 3 from 26 pulsars, mostly in double NSs; 12]. In 2010 and 2013, N ≃ were found in binary pulsars with white dwarf (WD) companion ⊙ nuc ⊙ ρ 0.04 M ± pulsars (MSPs, 249 catalogued with spin periods shorter tha [1.35 ⊙ Recently, Özel & Freire [9] compiled NS mass (and radius) mea The maximum mass that a neutron star (NS) can sustain, M The maximum mass of a NS depends on the compressibility of its The NS mass distribution has evolved as new types of NSs in bin MSPs (black-widows and redbacks) have notdistribution, been perhaps included due in to their m past scarcitythe or strong in irradiation order of the companionNSs star presently by known the pulsar in wi lightargue are of key recent to constraining findings M and including binary MSPs known in the Galactic field at the time (see Sectio the NS mass distribution.that Thanks NS to masses these span and a other wide previous range, between 1.2 and at least 2 M Super-Massive Neutron Stars 1. Introduction: the maximum neutron star mass is classified as a black hole if its mass exceeds M across multiple research fields,(GW) including astronomy. astrophysics, From n aand stellar-mass purely black observational holes in viewpoint, binary the systems is often base and they established that NSs can be as massive as 2 M still uncertain physical mechanisms taking place in supern during the gravitational collapse of a massive star [2]. Lat significantly increase the mass of a NSmagnetic via field, accretion, during as the well so-called recyclingregained stage interest [3]. in the Mo context of doubleSimply neutron put, star what merg is leftand after on two the neutron maximum stars mass merge that depend a neutron star can hold [e.g., 5]. evidence for a NS with more than two Solar masses, 2.40 EoSs) is needed to support more massive NSs. Microscopicall of state (EoS, the relationsaturation density between ( pressure and density) at from binary mergers. well enough to distinguish between their masses measured. The majority ofpulsars NS mass in measurements binary systems (299millisecond listed at the ATNF catalog, v1 set by the nucleon-nucleon interactions in thesix central decades part of research [6]. Therefore,physics, the as maximum it mass places of direct a constraints on the EoS of matter These were accurate measurements ( masses close to 2 M Two decades ago, the first measurements1.4 suggested M a single an PoS(MULTIF2019)023 ause of as “black RB (TBC) BW (TBC) Manuel Linares 1 Field RedBack PSRs 1 Field RedBack 14 Field RedBack PSRs 3 Field BlackWidow PSRs 3 Field BlackWidow 29 Field BlackWidow PSRs ries a day and form two distinct ordinates of the compact binary med + 11 candidates). Black squares mpanion, and are sometimes referred on star in the systems known as “red- 45 90 135 45 90 135 vely. Open symbols show candidate systems, reported yet. 0 0 2 60 30 60 30 -30 -60 -30 -60 315 315 Galactic longitude (deg) Galactic longitude (deg) ). They have been nicknamed after cannibalistic spiders bec ⊙ ), or a very low-mass “ultra-light” companion in those known 270 270 ⊙ 0.01 M ∼ 0.1 M c & c 225 225 All-sky map (Mollweide projection) showing the Galactic co

2008: 2019:

Compact binary MSPs have orbital periods shorter than about Galactic latitude (deg) latitude Galactic Galactic latitude (deg) latitude Galactic widows” (BWs; M the destructive effect that the pulsar wind may have on its co populations, with either a low-mass main-sequencebacks” compani (RBs; M MSPs known in 2008and (top, red 4 circles systems) show black-widow and andwhere 2019 redback the (bottom, MSPs, detection respecti 43 of a confir radio/gamma-ray pulsar has not been 2. A spider revolution: millisecond pulsars in compact bina Figure 1: Super-Massive Neutron Stars PoS(MULTIF2019)023 -LAT 3 kpc) and Fermi . Manuel Linares ). This allowed us ), a very important 2 K). Imposing these δ , γ , 470 280 β + − .14 hr orbit, PSR J2215+5135, hout the orbit using a suite of =8080 class of nearby (d ctive mass transfer, spiders are own in Figure 1 (top). These ex- D radiated companion star [18; 39]. r lines (H ures differ from ours and have no vealed new compact binary MSPs, were able to find a new and subtle articular, we found that magnesium ities than hydrogen lines, which are , among other fields, this new MSP /BWs [21] but are typically unsuited Ss in compact binary MSPs may be al measurements of the MSP mass, llar extinction is low, they are well meter) in order to collect high-quality s atmosphere, metallic lines trace the ning high signal-to-noise photometry mass of the star (K 35; 36; 37], this has turned s from independent dynamical studies ight sources at GeV energies, the band igns [24; 25; 26; 27; 28; 29; 30; 31] as rradiation of the inner side of the com- K to T straints are critical to measure robustly ary systems. he light and radial velocity curves in or- gamma-ray telescope in 2008, only four the reader is referred to Linares, Shahbaz decade, from 4 to more than 40 (Figure 1, ith brighter companion stars). This allows ) pulsars has emerged. Because most new 260 380 1 + − − Fermi 3 erg s =5660 and the NS mass distribution. N 35 0.1–100 GeV; [22; 23]) is providing unprecedented 2.5) and the masses of both stars. While our work was ∼ ± max NS –10 ◦ 34 10 ∼ ˙ E ’s large area telescope (LAT, Fermi In 2014, we set out to measure the mass of a redback pulsar in a 4 Surprisingly, many of these LAT-driven discoveries have re Furthermore, we measured the temperature of the star throug Super-Massive Neutron Stars collectively as “spiders”. Before the launch of the energetic (spin-down luminosity to find empirically and robustly the velocity of the center of compact binary MSPs were known include the MSPs field in of globular the clusters, Galaxy, which as now sh for contain dynamical 12/18 RBs mass measurements. Pulsars arewhere relatively br which had previous evidence forWe a observed massive the NS system and a withand strongly three including ir the optical Gran telescopes, Telescopio Canarias obtai (GTC, 10.4-mspectra dia throughout the orbit. Thankseffect: to among these the GTC absorption spectra linesunheated we from “cold” the side companion of star’ the starformed and predominantly thus on move the at inner higherlines “hot” veloc (MgI side triplet of at the 5167-5184 star. Å) In move p 10% faster than Balme 3. A 2.3 Solar-mass neutron star in PSR J2215+5135 sensitivity. Combined with targeted radio observingwell as campa optical and multi-wavelength follow-up [32;into 33; a 34; true “pulsar discovery machine”. so their population has increased drastically overbottom). the past This is what we may call “a spider revolution”: a new for spectroscopic studies of the companion star and dynamic spiders are also farwithin from reach of the optical telescopes Galactic (especially redbacks, plane, w where interste as detailed below.thought During to a accrete long mass from (Gyr)significantly their formation more companion phase massive stars, than so with that they a population N were is at having birth a strong [38]. impact Thus on M being completed, Romani et al.of reported PSR higher J2215+5135 inclination [40; 41].uncertainties, we Because concluded their that reported accuratemasses temperat temperature and inclination. con For the full details and discussion der to obtain the orbital inclination (i=63.9 & Casares (2018, [19]). independent temperature constraints, we modeled jointly t step to obtain reliable mass measurements in irradiated bin absorption lines and confirmed quantitatively thepanion extreme produced i by the pulsar wind (from T PoS(MULTIF2019)023 1 Manuel Linares proposed equa- R J2215+5135, with nts, including 17 compact ferent nights with the WHT and ource (unlike previous work [41]). of irradiated compact binaries. No s of matter in the core. It is worth J2215+5135 [39; 40]. Summarizing, this, together with our new empirical barrier factorily these three-band light curves t necessarily produced by an extended even if heating/irradiation of the com- SR J2215+5135 are “well behaved”, in ily shows that redback and black widow e on timescales of days to years (within the almer and MgI) assuming point-like ir- ⊙ 0.5 and green squares for the i, r and g bands, ave been detected (see, e.g., multi-epoch ; [39]). The orbital light curvesof this redback n the orbital phases, we did not find in our rror bars on the right). nes show the light curves measured by Schroeder i (2010-11) r (2010-11) g (2010-11) 4 i (Aug.2014) i (Sep.2014) r (Aug.2014) r (Sep.2014) g (Aug.2014) g (Sep.2014) Orbital phase measurement robust. ⊙ 0 , makes the 2.3 M 2 [19]. A 2.3 Solar-mass neutron star rules out most currently ⊙ 0.16 M ± Optical light curves of PSR J2215+5135 taken during four dif

Figure 3 shows an updated compilation of 86 NS mass measureme =2.27 We thereby found one of the most massive NSs known to date in PS

20 19 Magnitude (g, r, i-0.2) r, (g, Magnitude NS tions of state, castingstressing doubt here on that the the optical existencethe light of curves sense exotic and that spectra form they of onlyflares, P long-term show variability the or orbital transient modulationlight emission curves typical lines in Figure h 2). We(g,r,i) were as able to well fit as jointly the andradiation satis two-species by radial the velocity curves pulsar (B Furtermore, wind, after without carefully considering any the extended uncertainty heating i s in our optical study of thispanion particular by redback the we MSP found is extreme: that region i) and it iii) is it not shows variable, little ii)method or it to no is determine asymmetry. no K We argue that data significant asymmetry in the optical lightcurves of PSR 4. Super-massive neutron stars: breaking the 2 M binary MSPs ([9; 20; 45], and references therein). This read respectively) and September (gray symbols), 2014. Solid li available data and its photometric precision, shown by the e IAC80 telescopes on August (red triangles, magenta& circles Halpern in 2011 (3 years earlier,MSP convertedfrom are BVR smooth filters (down to the shortest 60 s exposures) and stabl M Figure 2: Super-Massive Neutron Stars PoS(MULTIF2019)023 3 3 Manuel Linares Stars X-ray Double Pulsars Neutron Binaries Binaries Bursters (LMXBs) (HMXBs) (Spiders) MSP+WD MSP+MS/UL easurements compiled by 2.5 2.5 es, as indicated; arrows show lower ) ⊙ 2 2 e et al. [45] is shown in blue. ifferent types of binary NSs are noted with labels 5 1.5 1.5 1 1 Neutron Star Mass (M 0.5 0.5 Blackwidows Cromartie'19 Redbacks Ozel&Freire'16 J1306-40 ; [42; 43; 44; 19; 15; 20]). For comparison, we show 68 NS mass m B1957+20 J1311-3430 J2129-0429 J1723-2837 J1622-0315 J2339-0533 J1048+2339 J2215+5135 J1301+0833 J1816+4510 J0212+5320 J1023+0038 J0740+6620J0740+6620 J2039.6-5618 J1417.7-4407 J0427.9-6704 J0846.0+2820 NS Masses of 17 compactbinary MSPs (red circles and black squar 0 0 Özel & Freire ([9], gray circles;along see the references right therein). side. The D recent NS mass measured by Cromarti limits on M Figure 3: Super-Massive Neutron Stars PoS(MULTIF2019)023 ider- ) NS ensitive to Manuel Linares (hr) Ref. (M ited by optical flares and orb limit. In Table 1 we collect XB) Vela X-1 has also been ⊙ ynamical measurements of the M ry MSP [49], the original black al. report a NS mass in the range ghest NS mass measurement, with s briefly these super-massive NSs, at is the maximum NS mass. confidence level (ranges indicate mass s velocity (estimated from a combi- mass measurement/constraint. Compact r final analysis of the light and radial 4% 115.2 [45] σ high-mass X-ray binary; MSP+WD: millisec- 19% 164.6 [9; 46] 15% 493.2 [9; 48] atics, most measurements indicate that 20% 1.6 [44] 15% 5.5 [20] 2, which the authors take from earlier ; see their Section 5). An independent curves, in light of recent results, should ± e 1- , giving the original references and some ◦ ⊙ lination. We give latest reported range from Özel & lination. We give latest reported range from Özel & ) Mean error P b c e d ates that this WD identification is uncertain). ⊙ 10 09 . . 37 25 range from a discussion of possible systematics, so this is . . 0 0 0.16 7% 4.1 [19] 0.04 2% 2.5 [14] 0.12 5% 9.2 [15] 0.16 8% 215.1 [47] [47]. Even though the optical determination of 0 0 ⊙ (M 6 + − + − ± ± ± ± ⊙ NS comes from optical light curve modelling only, without cons M NS 0.16 M . . ± ⊙ ⊙ a : 2.12 0.21 M 0.19 M ⊙ ± ± , but authors give 1.8–2.7 M ⊙ range). [15]. As discussed by van Kerkwijk et al., this result may be s σ ⊙ 0.45 M range was 2.74 range was 2.08 ± σ σ and argue that the accuracy of this measurement is partly lim 0.12 M ± ⊙ Super-massive neutron stars, sorted in order of increasing PSR J2215+5135 RB 2.27 NamePSR J0348+0432 MSP+WD 2.01 Type PSR B1516+02B MSP+WD? 1.5–2.2 PSR B1957+20 BW 2.40 3FGL J2039.6-5618 RBc 2.04 Vela X-1 HMXB 2.12 PSR J1748-2021B MSP+WD? 2.1–2.9 PSR J0740+6620 MSP+WD 2.14 PSR J1311–3430 BW 1.8–2.7 Formally 2.25 Note this is a probabilistic constraint assuming random inc =2.40 As mentioned in Section 1, the first-discovered compact bina The mass of the X-ray pulsar in the high-mass X-ray binary (HM RB: redback; RBc: redback candidate; BW: black widow; HMXB: Candidate RB, no pulsar detected yet. This M Note this is a probabilistic constraint assuming random inc e c d a b NS a mass constraint (not a 1- Freire. Original 1- systematic uncertainties on the orbitallight inclination curve (i=65 modelling results; [50])nation and of on simulated the spectra center andanalysis of analytical and mas arguments joint modeling ([15] of thebe light able and to radial establish velocity or updatevelocity this curves mass of measurement. the black In widow1.8–2.7 thei PSR M J1311-3430, Romani et the companion’s velocity may suffer from additionalthis system HMXB hosts a massive NS [51; 52]. In globular clusters, d widow pulsar PSR B1957+20, holds theM current record of the hi variable wind emission lines [44]. found to be higher than 2 M Super-Massive Neutron Stars MSPs (or “spiders”) tend to push the NS mass range beyond the 2 ond pulsar with white dwarf companion (a question mark indic and argue that compact binary MSPs are key to establishing wh Table 1: details on each mass measurement. In the following we discus constraints rather than actual measurements). binary MSPs (spiders) are shown in boldface. Errors are at th those systems with NS mass measurements above 2 M ing radial velocities. Freire. Original 1- PoS(MULTIF2019)023 ⊙ ⊙ ⊙ ee also . 0.22 M 0.04 M ⊙ ). Because ± ± 2.6 2.6 ⊙ Manuel Linares M 1.96 are less certain. > 37 25 limit. Strader and . . 0 0 ⊙ NS max NS + − J0740+6620 another 2.4 2.4 HMXBs Spiders MSP+WD e the 2 M . This result comes from a than 10%, showing the different Double NSs ⊙ 2.2 2.2 All (err<10%) nd a NS mass of 2.01 432 (modeling the WD absorption sed solely on light curve modeling urement techniques is important to J1048+2339: M 18 constitutes a similar case: a mea- pulsars to be close to or above 2 M ) sively due to general-relativistic peri- lination is unknown, Freire et al. used s allowed highly significant detections 0.10 M ects in the mass determination (ideally, urement of the total mass in the binary or super-massive NSs [48; 46]. Precise ⊙ 2 2 ± he implications for M s limit can be improved with more precise , spiders have masses from 1.4 to 2.4 M =2.14 ⊙ NS 7 1.8 1.8 : M ⊙ Neutron Star Mass (M 1.6 1.6 , i.e., the measurement of the relativistic Shapiro delay (s NS 1.4 1.4 but with a relatively large statistical uncertainty (2.04 ⊙ 1.2 1.2 ; see [14]). Most recently, Cromartie et al. [45] found in PSR c 1 1 Histogram of the 44 NS mass measurements with errors smaller 0 0 4 4 2 2 8 8 6 6 12 12 10 10 Other redback MSPs have been found that may be close to or abov As mentioned in Section 1, Antoniadis and collaborators fou source classes. While double NSs cluster around 1.35 M collaborators set a rather high lower limit on the mass of PSR ([20]; as they note, the relativelydynamical large studies). uncertainty on The thi redback candidatesurement 3FGL close J2039.6-56 to 2 M Figure 4: Super-Massive Neutron Stars companion star are challenging, but there is also evidence f long-term timing of radio MSPs in wideof eccentric the binaries ha rate of advanceastron of precession, periastron. such If detections this lead advance to[16]. is an Even exclu accurate if the meas companion isprobabilistic undetected arguments and to the orbital constrain inc the masses of two such (PSR J1748-2021B and PSR B1516+02B, see Table 1). pulsations have not been detected(without and radial velocity this measurements measurement available is so far), ba t different method to measure M super-massive NS with a mass above 2 M using pulsar timing and opticallines to observations find of M PSR J0348+0 [13; 53]). Finding super-massiveestablish NSs their with maximum mass, independent and meas to ruleapplying out these systematic different eff techniques to the same pulsar). PoS(MULTIF2019)023 54 Phys. and the ]. state from and act binary Initial of 2023+338. max NS pulsars, ARAA (2006) 327 18-20 mag) to Manuel Linares GS Inspiral, Stars Hole ∼ 56 radio sive [12; 8; 16; 9]. Stars, Star equation of collaboration, ]. Black 1710.05938 for transient Neutron Developments class Science and of Neutron ng only mass measurements Neutron of X-ray new ]. Star uper-massive NSs with masses ewly discovered nearby redback (1994) L5. Mass A Prognosis the Particle (1960) 393 . and this number may well increase (2017) L19 [ therefore constraining M State out of the 86 systems presented in ntially super-massive NSs shown in Binary ical band (typically Theoretical 271 11 w a narrow mass distribution centered a s. of and OLLABORATION Cyg, t decade, as they have moderately low- 850 Neutron C Stars: from Maximum The V404 Physics ApJL IRGO MNRAS Nuclear the observations: Equation of of V of 8 Waves the star., star Compact arXiv:astro-ph/0612440 astro-ph/9510136 in studies Annals and Review GW170817, Constraining Neutron of Radii, Matter companion Optical Gravitational ]. Annual densities, of (2007) 109 [ the (1996) 834 [ ]. Dense of high OLLABORATION AND Masses, 442 457 C at (Table 1). Here we stress that the growing population of comp Observations speed ⊙ ApJ (2017) 161101. Constraints, Observation 1603.02698 Matter PhysRep (1982) 728. and that recycled fast-spinning MSPs are on average more mas 119 ⊙ CIENTIFIC rotation 300 Function, Lett. The astro-ph/0608360 constraints, Observational [ GW170817: Rev. Multi-messenger Mass Nature IV. (2016) 401 [ To summarize, we show in Figure 4 a histogram of NS masses, usi [1] J. Casares and P. A. Charles, [3] M. A. Alpar, A. F. Cheng, M. A. Ruderman and J. Shaham, [6] E. Salpeter, [4] LIGO S [9] F. Özel and P. Freire, [5] B. Margalit and B. D. Metzger, [2] F. X. Timmes, S. E. Woosley and T. A. Weaver, [8] J. M. Lattimer and M. Prakash, [7] D. Page and S. Reddy, pursue high S/N spectroscopy and detailed dynamical studie References EoS of ultradense matter. Indeed, 4Table 1 of are the redbacks 9 (one systems of withas them pote the candidate) or population black of widows, compactMSPs, binary in MSPs particular, continues hold to themass grow. greatest companion potential N stars for which the are nex sufficiently bright in the opt During the past decade,in we the have range found 2–2.5 mounting M evidence for s MSPs shows great potential for finding super-massive NSs and with fractional uncertainties belowFigure 10% 3). (which It has includes been already 44 pointedaround out 1.35 that M double NSs sho Super-Massive Neutron Stars 5. Conclusions PoS(MULTIF2019)023 ]. ]. PSR 760 ApJ Star Birth arXiv (2019) A and ApJL National B1957+20, Optical Lines 872 Pulsars, Manuel Linares Neutron (2015) 23 1304.6875 Fermi PSR 1805.08799 Catalog, ApJ 218 Radio ]. (2010) 1081 Telescope I. Distribution Massive Companion, Pulsar a Magnesium Source ApJS 467 Energetic Binaries, (2013) 448 [ (2018) 54 [ Mass for Side: Australia Hessels, F. Camilo, M. A. Helium 340 s and J. W. T. Hessels, Four the Fourth ko, J. Greiner, A. Rau et al., 859 ]. Nature Pulsar Catalog, to at Lynch, M. H. van Kerkwijk et al., tt, C. C. Cheung et al., The On ]. Dark , ApJ Measurements. Black-widow at Evidence delay, the Science the Source ]. ]. catalog Flyweight Telescope Mass to a astro-ph/0412641 into catalog 1201.1006 Millisecond Shapiro Third Counterparts Star Binary, Area 9 with 1302.1790 Online J2215+5135, Peering Online using Star Large PSR Optical Redback Companion Neutron 1902.10045 (2012) 55 [ (2005) 1993 [ Pulsars, in ]. Telescope of the the Relativistic Fermi 757 (2013) 108 [ of 129 of Neutron Clusters, Star measured Area AJ ]. ApJ 769 star Study Compact Large Millisecond ApJ a Neutron 1009.5427 Globular Stars, ]. Discovery Demographics in in arXiv:astro-ph/9803260 ]. neutron Heavyweight Fermi Catalogue, ]. and A 1210.6884 Pulsars, Galactic Massive Pulsar Neutron a Pulsars (2011) 95 [ Pulsar of Radial-velocity a 728 (1999) 288 [ 1812.04626 Massive 1501.02003 1010.5788 McLaughlin et al., (2012) L36 [ 42 [ [ [ e-prints (2019) arXiv:1902.10045 [ Spectroscopy http://www.naic.edu/pfreire/GCpsr.html (2019) . Millisecond Establish J1311-3430: from ApJ Masses 512 A two-solar-mass Facility http://astro.phys.wvu.edu/GalacticMSPs (2019) . [16] F. Özel, D. Psaltis, R. Narayan and A. Santos Villarreal [20] J. Strader, S. Swihart, L. Chomiuk, A. Bahramian, C. Bri [23] The Fermi-LAT collaboration, [17] R. W. Romani, A. V. Filippenko, J. M. Silverman, S. B. Cen [14] J. Antoniadis, P. C. C. Freire, N. Wex, T. M. Tauris, R. S. [22] F. Acero et al., [18] R. P. Breton, M. H. van Kerkwijk, M. S. E. Roberts, J. W. T. [21] P. Freire, [19] M. Linares, T. Shahbaz and J. Casares, [13] P. B. Demorest, T. Pennucci, S. M. Ransom, M. S. E. Robert [12] S. E. Thorsett and D. Chakrabarty, [11] D. Lorimer, [15] M. H. van Kerkwijk, R. P. Breton and S. R. Kulkarni, Super-Massive Neutron Stars [10] R. N. Manchester, G. B. Hobbs, A. Teoh and M. Hobbs, PoS(MULTIF2019)023 ]. The ApJL Radio in The High Three Physics Parkes optical pulsars, of Low Pulsar, The Unassociated Manuel Linares Data the Pulsar Search (2012) L25 1411.1288 1205.3089 (2011) L16 Millisecond New and ]. 754 Fermi -Ray A Institute γ 727 Discoveries, Pulsar in ArXiv millisecond Radio Millisecond pulsars ApJL Description, ApJL five for Pulsar GBT Fermi ]. (2015) 4019 [ su, C. C. Cheung et al., of Probable ik, M. T. Wolff et al., American the Banaszak, C. M. Biwer et al., Ray, P. Bangale, S. M. Ransom Club, Spolaor, N. D’Amico et al., f 1408.2886 The of tacharyya, F. Camilo et al., C110509; N. D. R. Bhat et al., , H. T. Cromartie et al., 446 Survey recycled J1653.6-0159: Sources I. Sources, with Widow-like Series, M. Burgay, N. D’Amico, ]. five Widow eConf Millisecond -ray Discovery - , DOI. Pulsars: of γ 2FGL ]. 1406.5214 MNRAS Bright II. Black Survey. Pulsars and - Companion (2014) L20 [ a Black Fermi as Search 10 and the 793 Conference ]. Pulsar Discovery Survey Sources (2014) 67 [ 1507.04451 Faint proceedings 1101.1742 Blind Orbit 1111.3074 Joins Object Cap ApJL Virginia (2016) . companions, XI. Millisecond 50 Unassociated - 791 of Physics and Pulsar of The of New Fermi LAT ]. ApJ dwarf 1101.4778 Periods, (2015) 85 [ survey Celestial for Gamma-Ray Symposium Survey Sources (2011) L26 [ Fermi white Universe 810 ]. J1311.7-3429 University Institute Results, in Binary 743 GBT LAT Fermi Fermi Universe Northern Unidentified of 1201.3629 survey Searching 2FGL Journal ]. ]. Thesis, Initial (2011) 2455 [ an ApJL 2011 of Pulsar Pulsars Fermi Series, pp. 40–43, 2011, Resolution Bank American of and of 416 PhD 1205.3089 350-MHz Searches A Resolution Time Green (2012) L3 [ 1207.1736 1012.2862 [ et al., Evaporating J2339-0533, Discovery 747 Time detectability Sources, Radio Astrophysical The Analysis, MNRAS Searches Consortium, (2012) [ Millisecond High Pulsars, in P. Esposito, A. Pellizzoni and A.Conference Possenti, eds., vol. 1357 o [ [35] R. W. Romani, A. V. Filippenko and S. B. Cenko, [29] F. Camilo, M. Kerr, P. S. Ray, S. M. Ransom, J. Sarkissian [34] R. W. Romani, [28] K. Stovall, R. S. Lynch, S. M. Ransom, A. M. Archibald, S. [33] A. K. H. Kong, R. H. H. Huang, K. S. Cheng, J. Takata, Y. Yat [30] S. D. Bates, D. Thornton, M. Bailes, E. Barr, C. G. Bassa, Super-Massive Neutron Stars [24] J. W. T. Hessels, M. S. E. Roberts, M. A. McLaughlin, P. S. [32] R. W. Romani and M. S. Shaw, [27] P. S. Ray, A. A. Abdo, D. Parent, D. Bhattacharya, B. Bhat [31] S. Sanpa-Arsa, [25] S. M. Ransom, P. S. Ray, F. Camilo, M. S. E. Roberts, Ö. Çel [26] S. D. Bates, M. Bailes, N. D. R. Bhat, M. Burgay, S. Burke- PoS(MULTIF2019)023 ]. – Star Eight 577 binary Period a A pulsar, 809 A of of (2017) Redbacks A&A Extreme Neutron pulsar Short Manuel Linares 0711.0925 (2014) 78 ApJL of eclipsing Companions, 465 the and (2013) 27 of an 793 millisecond 775 Discovery (2016) 143 binaries, in Massive Binary, ]. Widow A ApJ J1301+0833: Widows Spectroscopy Study ApJ 833 millisecond MNRAS (2008) 670 [ X-ray ]. ]. pulsar massive PSR Companions ApJ Stars, Black essels, Keck iuk et al., ]. Black 675 the of , Z. Arzoumanian, H. Blumer Pulsars, redback , Y. Fetisova and J. Puls, T. Hessels, L. H. Frey et al., of of ApJ z, J. Casares, C. Fariña et al., the high-mass 1503.05247 Neutron extremely Spectroscopic (2016) 138. of millisecond High-inclination J0212.1+5320, Heating 0712.3826 , A an 6441, 1708.07355 A NS 833 of Formation J0212.1+5320, Modeling 1904.06759 Millisecond 3FGL eclipsing Shock NGC ApJ and 11 High-mass Properties (2015) 115 [ ten 3FGL and orbit: Binary for of (2008) 1433 [ 804 (2017) 4287 [ Pulsar, Moderate-M 6440 ]. 21-h A 679 measurements ApJ a Intra-binary 472 masses ]. in Candidate: Observations Evidence Eclipsing ApJ NGC ]. delay and of in M5, MNRAS Black-widow Pulsar ]. a Pulsars: (1988) 237. J2215+5135: J1311-3430, decay, 1606.03518 candidate Shapiro Pulsars of ]. Cluster 333 ]. ]. 1502.07126 PSR Populations 1506.04332 Pulsar pulsar orbital Study Millisecond (2016) 7 [ Nature Astronomy (2019) arXiv:1904.06759 [ Millisecond J0212.1+5320, Widow 1609.02232 Globular Relativistic Millisecond Distinct 828 the 1609.02951 1308.4107 1401.7966 [ [ binary, New in Ephemeris, Black Nature Kinematic 3FGL ApJ 4602 [ Binary Millisecond (2015) L10 [ Two Redback millisecond et al., [ (2015) A130 [ [39] J. Schroeder and J. Halpern, [37] M. Linares, P. Miles-Páez, P. Rodríguez-Gil, T. Shahba [45] H. T. Cromartie, E. Fonseca, S. M. Ransom, P. B. Demorest [42] R. W. Romani, M. L. Graham, A. V. Filippenko and W. Zheng, [47] M. Falanga, E. Bozzo, A. Lutovinov, J. M. Bonnet-Bidaud [49] A. S. Fruchter, D. R. Stinebring and J. H. Taylor, [41] R. W. Romani and N. Sanchez, Super-Massive Neutron Stars [36] K.-L. Li, A. K. H. Kong, X. Hou, J. Mao, J. Strader, L. Chom [44] R. W. Romani, A. V. Filippenko and S. B. Cenko, [46] P. C. C. Freire, A. Wolszczan, M. van den Berg and J. W. T. H [38] H.-L. Chen, X. Chen, T. M. Tauris and Z. Han, [40] R. W. Romani, M. L. Graham, A. V. Filippenko and M. Kerr, [43] T. Shahbaz, M. Linares and R. P. Breton, [48] P. C. C. Freire, S. M. Ransom, S. Bégin, I. H. Stairs, J. W. PoS(MULTIF2019)023 or tem eriod Vel, to do it The stars., The GP .g. Chen et Millisecond in Manuel Linares e companion is (2007) 1117 neutron of 379 Binary of oscillations masses MNRAS the . ⊙ ive NSs in general): how much of lems, T. R. Bedding et al., rres, M. E. Beer and R. A. On M non-radial ]. . Nice, S. M. Ransom et al., Measurements B1957+20, induced ]. PSR ]. during their active accretion phase. This suggests to Geometric 12 ⊙ tidally and and Mass X-1 companion . 1603.00545 ⊙ Set: the Vela Are the orbital period and the companion star’s rotational p of a) Is there any correlation between pulsar mass and other sys Some quark-based equations of state for the NS core do allow f in >2 M Data arXiv:astro-ph/0301243 astro-ph/9505071 NS star curve Yes, hyperons seem ruled out but deconfined quarks may be able Yes, as a result of tidal forces the orbits are circular and th a) Not that we know of. b) According to evolutionary models (e (2016) 167 [ ]. light 832 Nine-year neutron (2003) 313 [ (1995) 497 [ The ApJ the 401 303 of 0705.2514 NANOGrav Pulsars, mass A&A A&A [ Gibbons, [52] H. Quaintrell, A. J. Norton, T. D. C. Ash, P. Roche, B. Wil [53] E. Fonseca, T. T. Pennucci, J. A. Ellis, I. H. Stairs, D. J DISCUSSION JOSEP MARIA PAREDES: synchronized? MANUEL LINARES: “tidally locked”. SANDRO MEREGHETTI: parameters? b) In the casethat of mass PSR has J2215+5135 been (and accreted? super-mass MANUEL LINARES: al. 2013), redbacks can accrete up to 0.3–0.5 M that the pulsars would have to be born massive to go beyond 2 [51] M. H. van Kerkwijk, J. van Paradijs and E. J. Zuiderwijk, Super-Massive Neutron Stars [50] M. T. Reynolds, P. J. Callanan, A. S. Fruchter, M. A. P. To MANUEL LINARES: (especially in the most recent quark EoSs). super-massive NSs with M ANDREA SANTANGELO: