SN 2008ha and Low-Luminosity Transients Ryan Foley Clay Fellow Center for Astrophysics Stellar Death & Supernovae Collaborators Kirshner, Challis, Friedman, Rest Filippenko, Li, Chornock, Ganeshalingam, Silverman, Steele Brown Jha Wood-Vasey SN 2008A 1 arcmin – 50 – – 56 – Lick 40” V-band -20 B -19 NGC 634 DSS January 12, 2008 -18 SN 2002cx Had Low Velocities2005hk and Figure 1: Image of SN 2008A from the Lick Observator-17y 1 m Nickel telescope (left) compared to the pre-explosionLowDS SLuminosityimage (right). -20 – 50 – -19 V -18 – 56 – -17 Exceptional SN Ia that did not follow the Phillips relation -20 B -19 I max -18 Many odd characteristics, M 2005hk -17 including low line velocities -20 1.0 -19 VJ Large group (~16 objects) of -19 -18 ) + constant similar objects SN 2002cx ! -17 SN 2002cx (+25 days) -20 Log (f See Jha’s talk for more I SN 2005hk (+24 days) -19 H 0.1 SN 2008A (+28 days) max -18 M -18 SN 2008A -17 4000 5000 6000 7000 8000 9000 -20 0.8 1 1.2 1.4 1.6 1.8 2 Rest Wavelength (Å) m (B) J -19 ! 15 -18 Adapted from Phillips et al. 2007 Figure 2: February 12, 2008 Keck spectrum ofFigSN. 14.—2008AThe abscolomparute magnietuddets oof anSNealoguesIa at maxiSmuNm 2002cxlight in theandBV IJH bands -17 SN 2005hk at similar epochs showing strikingplhomogeneitotted versus the ydec(llineefrt);ate pandarameabsoluter ∆m15(teB).opticalThe blackmtriagnangleituds arFeigSe.Ns8e.—in Cthoemparison of spectra of SN 2005hk at phases of -5, +13, +24, and +55 days with redshift range 0.01 < z < 0.1 whose distances were calculated from their host galaxy radial similar epoch spectra of SN 2002cx from LFC. The spectra are plotted on a logarithmic flux of SN 2008A and SN 2005hk showing these arevelocouitietlierss in the-20cocomparedsmic microwavetobackagrosampleund frame aofssumnormaling a HubbSNele constIaant of H = 72 scale an0d shifted by an arbitrary constant. The wavelengths of the spectra were shifted to km s−1 Mpc−1. The red circle in each panel corresponds to SN 2005hk.H (right; panel adapted from Phillips et al. 2007). -19 the SN rest frame using the heliocentric velocities of the host galaxies given in NED. -18 -17 0.8 1 1.2 1.4 1.6 1.8 2 !m (B) 4 15 Fig. 14.— The absolute magnitudes of SNe Ia at maximum light in the BV IJH bands plotted versus the decline rate parameter ∆m15(B). The black triangles arFeigS.N8e.—in Cthoemparison of spectra of SN 2005hk at phases of -5, +13, +24, and +55 days with redshift range 0.01 < z < 0.1 whose distances were calculated from their host galaxy radial similar epoch spectra of SN 2002cx from LFC. The spectra are plotted on a logarithmic flux velocities in the cosmic microwave background frame assuming a Hubble constant of H = 72 scale an0d shifted by an arbitrary constant. The wavelengths of the spectra were shifted to km s−1 Mpc−1. The red circle in each panel corresponds to SN 2005hk. the SN rest frame using the heliocentric velocities of the host galaxies given in NED. SN 2008A 1 arcmin – 50 – – 56 – Lick 40” V-band -20 B -19 NGC 634 DSS January 12, 2008 -18 SN 2002cx Had Low Velocities2005hk and Figure 1: Image of SN 2008A from the Lick Observator-17y 1 m Nickel telescope (left) compared to the pre-explosionLowDS SLuminosityimage (right). -20 – 50 – -19 V -18 – 56 – 466 LI ET AL. -17 Exceptional SN Ia that did not follow the Phillips relation -20 B -19 I max -18 Many odd characteristics, M 2005hk -17 including low line velocities -20 1.0 -19 VJ Large group (~16 objects) of -19 -18 ) + constant similar objects SN 2002cx ! -17 SN 2002cx (+25 days) -20 Log (f See Jha’s talk for more I SN 2005hk (+24 days) -19 H 0.1 SN 2008A (+28 days) max -18 M -18 SN 2008A -17 4000 5000 6000 7000 8000 9000 -20 0.8 1 1.2 1.4 1.6 1.8 2 Rest Wavelength (Å) m (B) J Li et al. 2003 -19 ! 15 -18 Adapted from Phillips et al. 2007 Figure 2: February 12, 2008 Keck spectrum ofFigSN. Fig.14.12.—Evolution—2008AThe aofbthescoexpansionlomparute mvelocitiesagnieatsuddeduceddets oofromf anSseveralNealoguesabsorptionIa at mminima.axiTheSmuNmeasurementsm 2002cxlightofiSnN 2002cxtheandBareVshownIJwithH filledbancircles,ds and those of SN 1999ac-17are shown with open circles. The expansion velocities of the other SNe are taken or measured from Wells et al. (1994, for SN 1989B), SN 2005hk at similar epochs showing strikingplhomogeneitottFilippenkoed veretsal.us(1992b,theforydSeNc1991T),(llineefLeibundgutrt);ate pandetaral.a(m1993,eabsoluteforr SN∆1991bg),m15(teBFilippenko).opticalT(1997,he bforlaSNck1994D),mtriagnaLni egt all.eituds(1999,arFforeigSeN.Ns1997br),8e.—inandCthoLiemet parison of spectra of SN 2005hk at phases of -5, +13, +24, and +55 days with redshal.i(f2001b,t ranforgSeN 2000cx).0.01 <Notezthe<extremely0.1 wlowhoexpansionse disvelocitiestanceosf SwNe2002cx.re calculated from their host galaxy radial similar epoch spectra of SN 2002cx from LFC. The spectra are plotted on a logarithmic flux of SN 2008A and SN 2005hk showing these arevelocouitietlierss in the-20cocomparedsmic microwavetobackagrosampleund frame aofssumnormaling a HubbSNele constIaant of H = 72 scale an0d shifted by an arbitrary constant. The wavelengths of the spectra were shifted to km sfamily−1 Mofpexplosionc−1. Thmodels.e red Thecircfactle thatin eSNach1999acpanshowsel corresSNpo2002cxnds toandSNSN21999ac005hdatak.Hare shown with filled circles (right; panel adapted from Phillips et al. 2007). some similarities-19to SN 2002cx is suggestive of the latter and open circles, respectively. the SN rest frame using the heliocentric velocities of the host galaxies given in NED. hypothesis. -18 SN 2002cx has the lowest expansion velocities ever reported We also note that the spectral range 6500–8500 A˚ corre- for an SN Ia. For Fe iii l4404, Fe iii l5129, Fe ii l4555, and sponds to the b-17road R and I bands, so the peculiar spectral the Ca ii H and K lines, the measured Vexp of SN 2002cx is evolution in this region may be related to the unique photo- Ϫ6000 km sϪ1, only about half that of the other SNe Ia. The ∼ metric behavior of the SN0.8in the R and I 1bands. In particular1.2 , 1.4Vexp evolution1.6is also ver1.8y flat, implying2 that the velocity gra- the additional emission near 7000 A˚ may contribute to the broad!m dient(B)in the ejecta of SN 2002cx is small during the period of peak around maximum and the slow late-time decline in the 15spectral observations (t p Ϫ4 to 56 days). R4band, and the lack of strong Ca ii IR triplet absorption may No apparent Si ii l6355 or S ii ll5612, 5654 lines are Fig.contribute14.— toTthheeplateauabsoaroundlute mmaximumagnituanddestheosflowSNlate-e Ia aobsert mvedaxinimourumspectralighoft SNin 2002cx,the BbutV ItheJHexpansionbandve-s time decline in the I band. More discussion of the R-band and locity measured from these lines for other SNe Ia are shown plotted versus the decline rate parameter ∆m15(B). The black triangles are SNe in the I-band light curves can be found in § 4.3. in Figure 12 for completeness. Note thatFSNig.1999ac8.—hasCothemparison of spectra of SN 2005hk at phases of -5, +13, +24, and +55 days with redshift range 0.01 < z < 0.1 whose distances were calculated from their host galaxy radial lowest Vexp measured from S ii ll5612, 5654similineslar amongepoctheh spectra of SN 2002cx from LFC. The spectra are plotted on a logarithmic flux 3.6. Expansion Velocities velocities in the cosmic microwave background framseverale assuSNeminIagshowna HuinbbFigurele co12.nstTheantvaluesof H0of=Vexp72of −1 −1 scale and shifted by an arbitrary constant. The wavelengths of the spectra were shifted to km s TheMexpansionpc . Tvelocitieshe red(Vcexpir),casle inferredin eacfromh paobsernelvedcorresSNpo1999acnds tomeasuredSN 20from05htkhe. Fe ii and Fe iii lines are also minima of absorption lines in the spectra, may provide some lower than in SNe 1991T and 2000cx, althoughthe ShigherN rethanst finrame using the heliocentric velocities of the host galaxies given in NED. clue to the nature of SN Ia explosions (Branch, Drucker, & SN 2002cx. The similarity of the Vexp evolution between Jeffery 1988; Khokhlov, Mu¨ller, & Ho¨flich 1993). Figure 12 SN 2002cx and SN 1999ac is consistent with their similar shows the expansion velocities derived from several lines. The photometric behavior in the early B-band and V-band light 2003 PASP, 115:453–473 190 JHA ET AL. TABLE 1 Spectroscopic Observations of SN 2002cx Wavelength Range Resolution Exposure P.A. Parallactic Seeing UT Date (8) (8) (s) (deg) (deg) Air Mass (arcsec) 2003 Jan 07.65................. 3300–9430 6 2 ; 900 153.0 132.2 1.06 1.0 2003 Feb 27.66................ 3160–9420 6 800 66.0 67.3 1.28 0.7 2003 Feb 28.63................ 3160–5770 6 2 ; 2200 240.0 242.6 1.18 0.8 2003 Feb 28.63................ 6260–7540 2 2 ; 2200 240.0 242.6 1.18 0.8 has higher resolution than the others, so we have analyzed it February 27 and 28 observations correspond to 227 and 277 days separately. past B maximum light in the SN rest frame (Li et al. 2003b). We additionally show the latest SN 2002cx spectrum from the pre- 3. ANALYSIS AND RESULTS vious observing season, at an epoch of +56 days, presented by Li et al. (2003b) and analyzed in more detail by Branch et al. The late-time spectra of SN 2002cx, corrected to rest-frame 1 (2004a). For comparison we also display spectra of normal SNe wavelengths (with cz 7184 km sÀ for the host galaxy, CGCG Ia at similar epochs, including SN 1998aq (+52 days) and SN SN 2002cx-like Objects 044Form035; Falco et al.