From jop at astro.columbia.edu Mon Nov 4 06:14:06 2019 From: jop at astro.columbia.edu (Joe Patterson) Date: Mon, 4 Nov 2019 06:14:06 -0500 Subject: (cba:news) possible riches in ATel 13257 In-Reply-To: <201911040659.xA46xcAQ060368@inprodmail04.cc.columbia.edu> References: <201911040659.xA46xcAQ060368@inprodmail04.cc.columbia.edu> Message-ID: <373b2459-f96c-834e-250d-6cf3c279cab5@astro.columbia.edu> Hi CBAers, The object described in ATel 13257 could be quite interesting to us. It's seasonally appropriate, and at a sufficient galactic latitude (-20) to suggest (probably) no great problems in identification and/or interstellar absorbtion. It also gets more well-placed in the sky as time goes on. BUT since northern observers are shut out, it's important that southern observers jump to it! Based on the example of Maxie and others, the key signature right now - other than the previously reported X-rays - is probably the very rapid variations (seconds). Since *clouds* have a similar signature, it would be helpful if you included some comment about this worry, along with the time-series data you acquire. joe p -------- Forwarded Message -------- Subject: ATel 13257, 13258 Date: Mon, 4 Nov 2019 01:59:38 -0500 From: atel at astronomerstelegram.org To: jop at astro.columbia.edu ------------------------------------------------------------------------------ ------------------------------------------------------------------------------ The Astronomer's Telegram http://www.astronomerstelegram.org ------------------------------------------------------------------------------ Posted: Within the last 24 hours ============================================================================== ATEL #13257 ATEL #13257 Title: MAXI J0637-430: Swift localization, optical counterpart Author: J. A. Kennea (PSU), A. Bahramian (ICRAR), P. A. Evans, A. P. Beardmore (U Leicester), H. A. Krimm (CRESST/GSFC/USRA), P. Romano (INAF-IASFPA), K. Yamaoka (Nagoya U.), M. Serino (RIKEN), H. Negoro (Nihon U.) Queries: jak51 at psu.edu Posted: 3 Nov 2019; 19:10 UT Subjects:X-ray, Black Hole, Transient At 13:39UT on November 3, 2019, Swift performed a target of opportunity observation to observe the location of the newly discovered soft X-ray transient, MAXI J0637-430 (Negoro et al., ATEL #13256). Swift performed a 7-point tiling of the MAXI error region with an exposure of 200s per tile. In the Photon Counting mode data, we find a previously uncatalogued bright X-ray source at the following location: RA/Dec(J2000) = 99.09828, -42.86780, which is equivalent to: RA(J2000) = 06h 36m 23.59s, Dec(J2000) = -42d 52m 04.1s, with an estimated uncertainty of 2.3 arc-seconds radius (90% confidence). This position lies 28.4 arc-mins from the 2-4keV MAXI localization, and 18.5 arc-mins from the 4-10 keV band MAXI localization. We note that the XRT position is consistent with the hard band localization, but not the soft band. However, the XRT detected source is bright and uncatalogued, suggesting that this is MAXI J0637-430. This transient is bright, with a count rate corrected for pile up of ~310 XRT count/s. The pile-up corrected X-ray spectrum can be well fit by an absorbed power-law + disk blackbody spectrum, with kT_in = 0.9 +/- 0.1 keV, and photon index = 2.3 +/- 0.8. Absorption with this model is ~8 x 10^20 cm^2. The observed flux is 1 x 10^-8 erg/s/cm^2 (0.5 -10 keV). In addition UVOT detects a source inside the XRT error circle, with a brightness of u = 14.87 +/- 0.02 (Vega). A Vizier catalog search does not reveal a known star at this localization, suggesting that this optical source has brightened significantly. We note that significant brightening (~5 magnitudes) of the optical counterpart during X-ray outburst is common for BH-LMXBs. The UVOT position is RA/Dec(J2000) = 99.09881, -42.86785, which is equivalent to: RA(J2000) = 06h 36m 23.23s Dec(J2000) = -42d 52m 04.25s. We encourage further observations of this source in optical and X-ray in order to determine the nature of the source. This work was supported by NASA Grant 80NSSC19K1383, awarded by the Swift Guest Investigator program. ------------------------------------------------------------------------------ Password Certification: Jamie A. Kennea (kennea at astro.psu.edu) http://www.astronomerstelegram.org/?read=13257 ============================================================================== ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Fri Nov 8 09:15:53 2019 From: jop at astro.columbia.edu (Joe Patterson) Date: Fri, 8 Nov 2019 09:15:53 -0500 Subject: (cba:news) QR And, finis Message-ID: <9bbe584c-b8f6-a93d-6560-b2a45bc1ab38@astro.columbia.edu> Hi CBAers, Really nice light curve and precise eclipse timing this year (and last) for the supersoft source QR And. Time to finish for the year, and write it up. Lotta familiar CBA names on this one (Gordon, Tonny, Joe U,, Shawn, John Rock), plus a few new guys. The supersoft sources are all great targets for orbital-period studies, because they - unlike practically all other CVs - show *rapid* period changes, which are diagnostic of mass transfer rates. For us, T Pyx pointed the way to this realization. Most of the world still does not recognize T Pyx as a supersoft... but every sunrise takes a while for light to dispel the darkness. The great valley of the Umzimkulu was once in darkness too, but, as Alan Paton predicted, the light came there eventually. joe p PS This is totally unreasonable, but a few snapshot magnitudes of the original MAXIE (MAXI J1820+070) would nicely conclude our 2-year program. It's probably somewhere around 18.5 and a few million airmasses west, so feel free to ignore! ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Thu Nov 28 10:25:59 2019 From: jop at astro.columbia.edu (Joe Patterson) Date: Thu, 28 Nov 2019 10:25:59 -0500 Subject: (cba:news) "Winter" stars for Dec-Jan Message-ID: <7bd01893-d3ed-8e07-64ed-397dca5de0b9@astro.columbia.edu> Dear CBAers, Many IPs lurking in the sky these nights. There are a few new ones to report... plus some old ones which have now revealed or should reveal a period change (due to the torques exerted by the accreting gas). The latter take at least a few years to detect (white dwarfs have a decently large moment of inertia), but we've been pounding away for a while, and the pulses eventually start to arrive EARLY by measurable elements ("early" since most of the white dwarfs are spinning up from the torques). So I'm preparing a history-of-period-change paper. Some well-placed stars these days are: V418 Gem*, V902 Mon*, HT Cam*, HZ Pup*, WX Pyx*, BG CMi, V647 Aur, V1062 Tau*, V405 Aur. I've asterisked the stars I consider to be not yet "properly published", and therefore I guess deserving of somewhat higher priority. But the best single measure of priority is probably determined by the match to your individual circumstances: brightness, time of night, quality of night, crowded field, suitable comp, etc. It's best to choose 1, 2, or 3 of these stars - and specialize in them. Since the main interest here is *periods*, a clear filter is fine. A few LONG runs are very desirable, but runs as short as 2 hours are plenty useful too. The only really short period here ia 4 minutes (V418 Gem - though it has a menagerie of other periods which have never been clarified). On that one, you need to keep the cycle time (observing + readout) below one minute. This star has a raft of periods - fast and slow - and they've never been adequately identified, much less understood. Nearly all of these stars are in Koji Mukai's ("NASA's") page on intermediate polars, and Lew Cook's re-ordering of it. I didn't manage to make it to Las Cruces for the AAVSO meeting (been hobbling around with a torn Achilles)... but maybe someone could write with a summary of relevant goings-on? joe p ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/