THE ASTRONOMICAL JOURNAL, 117:2466È2484, 1999 May ( 1999. The American Astronomical Society. All rights reserved. Printed in U.S.A. THE SECOND EXT REME UL T RAV IOL ET EXPL ORER RIGHT ANGLE PROGRAM CATALOG D. J. CHRISTIAN,1 N. CRAIG,1 W. CAHILL,B.ROBERTS, AND R. F. MALINA Center for EUV Astrophysics, University of California at Berkeley, 2150 Kittredge Street, Berkeley, CA 94720È5030; damian=cea.berkeley.edu Received 1998 November 23; accepted 1999 January 22 ABSTRACT We present the detection of 235 extreme ultraviolet sources, of which 169 are new detections, using the Extreme Ultraviolet ExplorerÏs (EUV E) Right Angle Program (RAP) data. This catalog includes obser- vations since the Ðrst EUV E RAP catalog (1994 January) and covers 17% of the sky. The EUV E RAP uses the all-sky survey telescopes (also known as ““ scanners ÏÏ), mounted at right angles to the Deep Survey and spectrometer instruments, to obtain photometric data in four wavelength bands centered at D100A (Lexan/B), D200A (Al/Ti/C), D400A (Ti/Sb/Al), and D550A (Sn/SiO). This allows the RAP to accumulate data serendipitously during pointed spectroscopic observations. The long exposure times possible with RAP observations provide much greater sensitivity than the all-sky survey. We present EUV E source count rates and probable source identiÐcations from the available catalogs and literature. The source distribution is similar to previous extreme ultraviolet (EUV) catalogs with 2% early-type stars, 45% late-type stars, 8% white dwarfs, 6% extragalactic, 24% with no Ðrm classiÐcation, and 15% with no optical identiÐcation. We also present 36 detections of early-type stars that are probably the result of non-EUV radiation. We have detected stellar Ñares from approximately 12 sources, including: EUVE J0008]208, M4 star G32-6 (EUVE J0016]198), a new source EUV E J0202]105, EUVE J0213]368, RS CVn V711 Tau (EUVE J0336]005), BY Draconis type variable V837 Tau (EUVE J0336]259), the new K5 binary EUVE J0725[004, EUVE J1147]050, EUVE J1148[374, EUVE J1334[083 (EQ Vir), EUVE J1438[432 (WT 486/487), EUVE J1808]297, and the M5.5e star G208[45 (EUVE J1953]444). We present sample light curves for the brighter sources. Key words: catalogs È stars: late-type È ultraviolet emission 1. INTRODUCTION timing studies of cataclysmic variables (Howell, Sirk, & Malina 1995; Warren, Sirk & Vallerga 1995; Craig et al. Early Berkeley sounding rockets followed by the Extreme 1996), active galactic nuclei (Fruscione 1998), and detections Ultraviolet (EUV) telescope Ñown on board the 1975 of stellar Ñares (Christian, Drake, & Mathioudakis 1998). Apollo-Soyuz mission proved the feasibility of working in The Ðrst RAP catalog (McDonald et al. 1994) presented 114 the wave band between D100 and 900A (Margon et al. sources, 99 of which were new EUV detections. The long 1976; Lampton et al. 1976). These e†orts culminated in the observations possible with the RAP program allow a much Extreme Ultraviolet Explorer (EUV E), the Ðrst satellite greater sensitivity than the all-sky survey. The RAP is dis- dedicated entirely to the EUV wave band. The primary cussed in detail below. scientiÐc goals of the EUV E mission were to conduct a In this paper, we present results of the analysis of EUV E photometric survey of the entire sky over the EUV band, as RAP observations since the Ðrst RAP catalog, 1994 well as a more sensitive survey along the ecliptic (1992 JulyÈ January. We describe the RAP and instrument character- 1993 January). The survey period was followed by dedi- istics in ° 2. We present the observation selection criteria cated spectroscopy for selected EUV targets (from 1993 and analysis techniques in ° 3, and in ° 4 we present the January to the present). The EUV E all-sky survey detected catalog results in tabular form with explanations. In ° 5we 734 objects (Bowyer et al. 1996, hereafter Cat2). The EUV E discuss the distribution of source types, and in ° 6we source list has been expanded by correlating EUV E all-sky present light curves for a sample of bright sources, including survey detections from the Lexan bandpass centered at 100 Ñare detections from late-type stars. A with ROSAT PSPC detections (Lampton et al. 1997), thus raising the number of EUV E sources to over 900. The 2. OBSERVATIONS EUV E and ROSAT WFC surveys (Pye et al. 1995) have The Guest Observer (GO) phase of the EUV E mission shown the brightest EUV sources to be hot white dwarfs, has accumulated pointed observations of over 400 unique active and nearby late-type stars, cataclysmic variables, and sources since the initial phase of the all-sky survey was various types of active galactic nuclei. completed (from 1993 January to the present). The GO The number of EUV E sources has been further expanded pointed observations have primarily used the EUV Deep by serendipitous observations using the all-sky survey tele- Survey and Spectrometer (DS/S) telescope. However, scopes during pointed Guest Observer observations. EUV E pseudoserendipitous observations have continued through all-sky survey telescopes are mounted perpendicular to the this phase by using the survey telescopes, which are Deep Survey/Spectrometer (DS/S) telescope and provide mounted perpendicular to the DS/S in what has become serendipitous data during pointed DS/S observations. This known as the Right Angle Program (RAP). The source program has become known as the Right Angle Program detections from the Ðrst year of this program were present- (RAP). RAP data have provided valuable photometric and ed by McDonald et al. (1994), which covered observations through 1994 January. Table 3 of the second EUV E all-sky ÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈ catalog (Cat2) includes miscellaneous EUV E detections and 1 Eureka ScientiÐc Inc., Oakland, CA. RAP Ðrst catalog results though 1994 December; the selec- 2466 THE SECOND EUV E RIGHT ANGLE PROGRAM CATALOG 2467 tion criteria in Table 3 varies, and for this reason we include detections using the Deep Survey telescope. Details of the RAP results since 1994 January. One of the key advantages scanner and DS observations are discussed below. of RAP observations over the all-sky survey is that expo- 2.1. Scanning Telescopes sure times for each Ðeld observed on the sky are generally much longer because they are dictated by the DS/S point- The direction in which the scanning telescopes are ings. We have analyzed RAP pointings with a minimum pointed depends on two factors: the pointing direction of exposure time of 10 ks, to generally have signiÐcantly more the Guest ObserverÏs DS/S observation and the roll angle of exposure than the all-sky survey, which had a few hundred the spacecraft. While for a given DS/S observation the DS/S seconds per exposure at intermediate ecliptic latitudes. pointing is Ðxed, there is often considerable latitude in the Over 600 individual RAP pointings from 1994 January to choice of roll angles. Based on this latitude, the roll angle 1998 November were identiÐed. The almost 4 years of RAP can be chosen such that the scanners can acquire any pre- DS and scanner pointings included in this catalog cover viously known EUV target or new Ðeld that might lie within B17% of the sky with a exposure times of at least 10 ks. the allowed scanner Ðeld of view. The average exposure time is 55 ks with the 700 ks DS/S The scanners were designed to obtain data in three bands observation of 1H 0419[577 being the longest. We present during an observation. A source positioned in the Lexan/B an exposure map of the RAP DS and scanner Ðelds Ðlter (hereafter ““ Lexan ÏÏ) of scanner A will also appear in included in this work in Figure 1. the Al/Ti/C Ðlter (hereafter ““ Al/C ÏÏ) of scanner B and the The optics and Ðlters of the scanning and Deep Survey Sn/SiO (““ tin ÏÏ) Ðlter of scanner C. Similarly, a source posi- telescopes were designed to be sensitive to particular tioned in the Lexan Ðlter of scanner B will appear in the regions of the EUV spectrum (Bowyer & Malina 1991 and Al/C Ðlter of scanner A and the Ti/Sb/Al (““ dagwood ÏÏ) Ðlter Malina et al. 1994) and are listed in Table 1. Although our of scanner C. The scanner A Lexan quadrant developed a analysis concentrates on detections made with the scanning signiÐcant pin-hole early in the mission that caused about telescopes, it also includes initial results from serendipitous one-half of the right-side Ðlter quadrant to be unusable. For this reason later in the mission, known EUV sources TABLE 1 observed with the RAP were placed in the scanner B Lexan NSTRUMENT PECIFICATIONS AND ILTER ANDPASSES quadrant. Scanner C tin band has the largest background of EUV E I S 10% F B any instrument, because of geocornal lines of He I (584 A ) and placed a high demand on the available telemetry. The FOV jpeak Bandpass Instrument (deg) Filter (A )(A ) tin Ðlter of scanner C was turned o† after 1995 May to allow other instruments more telemetry bandwidth, and no Deep survey ............ 2 Lexan/B 91 67È178 tin data are available after this time. Al/C 171 157È364 Scanners A and B ...... 5 Lexan/B 89 58È174 2.2. Deep Survey Al/Ti/C 171 156È234 The Deep Survey/Spectrometer (DS/S) telescope also Scanner C............... 4 Ti/Sb/Al 405 345È605 provides the capability for serendipitous source detections Sn/SiO 555 500È740 during long GO pointings. The bandpasses of the DS 60o 30o 12h 6h 0h 18h -30o -60o FIG. 1.ÈAito† projection in equatorial coordinates of the sky coverage for RAP scanner and DS pointings presented in this catalog.